基于特殊螺纹密封完整性的三轴设计系数研究

针对高温高压气井完井油管柱密封完整性问题，开展了基于88.90 mm×6.45 mm 110SS材料油管一种气密封特殊螺纹密封完整性分析的管柱三轴设计系数研究，研究中采用了API RP 5C5—2017国际标准螺纹性能试验评价方法，进行了高温和室温环境下A系全包络线载荷密封实验评价。基于气密封能判据，采用有限元模拟分析了不同VME（冯米塞斯等效应力）全包络线载荷2次循环工况的密封能和密封能倍数的变化规律并确定了危险载荷点。结果表明，通过API标准密封完整性实验评价的气密封特殊螺纹连接，需采用有限元进一步分析包络线载荷循环密封能及密封能倍数的变化规律，确定这种螺纹连接安全适用范围；同时开展了3种VME全包络线载荷2次循环后密封适用性分析，确定了高温和室温两种环境下螺纹安全适用包络线载荷范围及合理的三轴安全系数，并完成了1口高温高压气井完井油管柱安全分析和现场应用。提出的研究方法为管柱三轴设计安全系数的确定提供了有益指导。

A Study on Tri-axial Design Coefficient Based on Seal Integrity of Premium Connection

Aiming at the sealing integrity problem of tubing string in high temperature and high pressure gas well completion, the research on the tri-axis design coefficient of string is carried out based on the integrity analysis of a premium connection of gas seal on the 88.90 mm×6.45 mm 110SS steel grade tubing. In this study, API RP 5C5-2017 international standard connection performance test evaluation method is used to evaluate the load sealing test of a series full envelope under high temperature and room temperature environment. The dangerous load point and variation laws of seal energy and seal energy multiple are analyzed after second-time full envelope load cycles with different full envelope load (VME95% and VME 90%) according to gas seal energy criterion. Results show the seal energy and seal energy multiple as well as its variation law have to be further analyzed under full envelope load cycle by FEA, by which the safety applicable envelope load range need to be determined, although the gas seal premium connection has been evaluated by API standard seal integrity test. Therefore, the serviceability analysis of sealing performance has been performed after second-time full envelope load cycles with three kinds of full envelope load based on the full envelope load test evaluation and finite element simulation, and the safety applicable envelope load range and reasonable tri-axial safety factor have been determined under high temperature and ambient temperature environment. The research results have been applied successfully in some HTHP gas well. The research method presented in this paper provides useful guidance for the determination of safety factor of tri-axial design of tubing string.